The use of bioabsorbable plates to repair bone fractures, particularly factures to the craniofacial skeleton is known. In this procedure, a bioabsorbable plate is used to hold bone together to allow a fracture to heal. The plate is generally formed to the bone and held in place by screws. Bioabsorbable plates are normally rigid, become soft or malleable when heated, and return to being rigid when cooled. Typically, a bioabsorbable plate is heated in some manner to make it easily deformable so that the plate can be formed to the bone. Either before or after the plate is formed to the bone, a drill is used to drill holes into the bone. The drilled holes are then tapped and screws are positioned within openings in the plates and threaded into the tapped holes to hold the plates in position.
One problem with known systems for applying bioabsorbable plates is that the plate doesn""t remain soft for long. Once it is heated, the surgeon must fairly quickly form the plate to the bone structure. If the surgeon doesn""t get the plate properly formed before it cools, then the plate must be heated again and the forming process started over. As should be appreciated, this can become a very tedious process and result in loss of time during the surgical procedure. Additionally, the surgeon has no means for spot heating the plate to deform a specific spot or portion on the plate to better conform the plate to the bone.
Another problem with known bioabsorbable plates is that the attached screws can create stresses within the plates. In the event that a screw is not threaded into a tapped hole in proper alignment, the screw may only contact the plate with point contact. In this event, the plate may crack or loosen due to the uneven force distribution. Obviously, this would be a problem, particularly if the problem is not discovered until after stitches have been applied.
A problem with known bioabsorbable screws is there tendency to break due to their design. Although bioabsorbable screws are very strong, they can break off while being threaded into the tapped hole or when being tightened. Once broken, the screw generally must be drilled out of the bone, a new larger hole drilled and retapped and a larger screw threaded into the tapped hole. Again, this is a tedious process and one which creates difficulties during an operation.
Another problem with known bioabsorbable systems are the techniques for heating the bioabsorbable plates. The most common method for heating the bioabsorbable plates is to place them in a hot water bath which sufficiently heats the plate for it to be deformable. Because the hot water bath has to be within the sterile field of the surgery room, it must be capable of being sterilized. Typically, the water bath amounts to a stand draped with a cloth and a sterilized bowl to contain hot water. The surgeon can then dip the bioabsorbable plates into the hot water and conform them to the bone surface.
Another problem with known surgical systems to fasten bioabsorbable plates to bone structure is the complicated system used to match a request by a surgeon for a particular plate with the actual template. Typically, extensively long alpha numeric codes are used which result in the possibility of confusion between the request by the doctor and the filling of that request by an attendant.
The present invention overcomes the above problems by providing a bioabsorbable plate that has a first thermo-chemical solid state which is rigid and a second thermo-chemical solid state which is deformable so that it can be easily formed to the bone. The plate includes a plurality of at least two openings for receiving a fastener with a relief area surrounding each of the openings to allow the fastener to seat within the bioabsorbable plate so that no part of the fastener extends above the surface of the plate when the fastener is applied. The relief area presents a generally concave surface surrounding each of the openings. The relief area provides a stable contact surface for the fastener. This reduces tensile stresses in the plate and allows proper seating of the fastener within the relief area when the fastener is inserted either properly or at an angle that is not perpendicular to the plate.
The fastener of the present invention includes a head and shank portion. The head contacts the bioabsorbable plate to hold the bioabsorbable plate against the bone surface to be repaired. The shank portion extends from the head portion and includes threads for providing threaded engagement with the bone surface being repaired. The head portion includes at least one recess for insertion of a driver to allow the fastener to be threaded into the bone surface being repaired. This head portion includes a bottom surface presenting a generally convex contour for contacting a concave relief within the bioabsorbable plate. This convex contour mating with the concave relief ensures that the screw head will have at least line contact with the plate and preferably surface contact. This enhances the fastening of the plate to bone and reduces if not eliminates the problem of tensile stresses in the plate due to misaligned screws.
In the disclosed embodiment of the fastener of the present invention, the head portion includes a pair of notches. The notches include a pair of side walls and a rear wall. The notches are oriented 180 degrees apart about the circumference of the head portion of the fastener. The notches are sized to receive features of the driver, and the side walls providing a contact surface for the driver to thread the fastener into place. The positioning of the side walls distributes forces applied to the screw through the head as compressive forces because the side walls are not through the centerline of the fastener. The side walls for each of the notches fall on lines that cross at a point outside the centerline of the head portion, thereby concentrating the forces exerted onto the head portion into compressive stresses within the head portion to reduce failure.
The present invention also includes a driver for threading the fasteners into bone. The driver includes an operative end for engagement with a fastener, a handle portion opposite the operative end for allowing manual manipulation of the driver to insert the fastener, and a clutch mechanism interconnecting the handle portion and the operative end for limiting the amount of torque that can be transferred. The handle portion includes a switch for selectively activating the clutch mechanism. The operative end includes a pair of fingers, each of the fingers including side walls and an internal wall. The side walls are spaced to fit within notches in the head portion of the fastener. The fingers have a thickness that is less than the depth of the notches on the fastener to allow the fingers to fit completely within the circumference of the head portion of the fastener to prevent interference with the bioabsorbable plate when the fastener is applied using the driver.
Another advantage of the present invention is the use of a unique portable bowl for containing a volume of heated fluid. The bowl includes a base, a reservoir for holding a volume of heated fluid, and a heating element disposed within the base for heating the fluid within the reservoir. A controller for controlling the heating element and maintaining the temperature of the heated fluid within the reservoir is located at a remote location from the bowl. In this way, the bowl can be easily sterilized without having to sterilize the more difficult to sterilize controller. The portable bowl includes a retractable cover assembly for keeping the heated fluid within the bowl and to assist in keeping the fluid at a predetermined temperature. The cover assembly includes features for holding tools to allow the tools to extend into the heated fluid within the portable bowl.
In addition to the portable bowl, the present invention includes an apparatus for applying a heated fluid to a localized portion of a bioabsorbable plate. The device includes a front end with a tip, a rear end, and a shaft portion interconnecting the front end and the rear end. A cavity is disposed on the tip to hold a droplet of the heated fluid to the tip when the tip is dipped within the heated fluid or to draw heated water into the cavity to be dispensed when desired. The tool allows a surgeon to heat the plate at a localized point without having to reheat the entire plate.
The present invention also includes a dispenser for holding and delivering fasteners to a point of use. The dispenser includes a tray for holding a plurality of fasteners, a lid mounted rotatably onto the tray for keeping the fasteners contained until used, and an opening to allow the fasteners to be removed from the tray. The tray has a plurality of apertures spaced radially about the tray. Each aperture is adapted to removably hold one fastener in vertical orientation. The lid includes a first opening and a second opening spaced to fall directly above the apertures when the lid is rotated and adapted to allow an operable end of a driver to be inserted into the tray to engage and remove the fastener from one of the apertures. There are a plurality of detents spaced radially around the outer circumference of the tray, the lid includes at least one indent for receiving one of the plurality of detents, so that the lid can be rotated between a plurality of radial positions. The detents are spaced such that as the lid rotates, the pair of openings within the lid move from a first position wherein the first opening is directly over one of the apertures and the second opening is positioned between two of the apertures, a second position where both the first and second openings are located directly above one of the apertures, and a third position wherein both the first and second openings are located between two of the apertures.
The invention further includes a device for handling bioabsorbable plates. The device includes a pair of flexible elongated arms in adjacent lengthwise relationship with one another, each arm having a first end and a second end. The first ends of the arms are secured to one another, with the second ends of the arms being disposed at a distance from one another. A generally flat protruding portion is attached to the second end of each of the arms, the protruding portions of each arm being oriented parallel to one another. This device allows the plates to be held without damage to the plates.
To assist in forming the plates to the contour of the bone surface, a template for capturing the contour of a bone structure to be repaired is provided. The template allows the plate to be pre-contoured, wherein the template presents a two-dimensional shape that roughly corresponds to the two-dimensional shape of the plate that is to be contoured. In the preferred embodiment, the template has indents that correspond to the locations of fastener openings within the plate. In the most preferred embodiment, the template is made from a malleable material which is autoclavable to allow the template to be sterilized and re-used. In another embodiment, the template is a block having a top and bottom surface, and including a plurality of through holes extending between the top and bottom surfaces. A plurality of pins are disposed within the holes. A locking device locks the pins within the through holes to prevent the pins from sliding therein. The position of the pins are changed when pressed against the bone structure to give a three dimensional view of the bone contour. The pins can then be locked in place and the plate deformed to the contour of the pins.
All of these items are preferrably contained within a kit that can be easily sterilized and taken to the sterile surgical field. Additionally, the present invention includes the method of using the above items to fasten fractured bone pieces together. Still further, the present invention includes a unique coding system to simplify the surgical procedure.